When you start leaning on the S58, you find out quick where the limits are. Big boost, ethanol blends, long track sessions, hot summer traffic, it all adds up. Coolant temps creep up and the car starts protecting itself. Power gets pulled and the fun fades. The CSF High Performance Auxiliary Radiator keeps your G8X M3, M4, or G87 M2 steady when things get serious. You stay in boost longer. You finish sessions without backing off. The car feels strong and consistent instead of heat soaked and tired.

CSF has been building radiators for over 50 years, and the G8X platform got the full treatment. These auxiliary radiators were developed to work with the complex S58 cooling system and tested on street builds and dedicated race cars pushing well over 1000 horsepower. Track abuse, dyno sessions, and real world heat cycles shaped the final design. The goal was simple. Increase capacity, improve heat rejection, and eliminate the weak plastic factory components.

Precision Engineered Design

Built around a 2 row 42mm high performance core, compared to the OEM 1 row 34mm unit. The larger core increases coolant volume and cooling capacity.

CSF exclusive B Tube technology increases heat transfer surface area by about 15 percent over traditional oval tubes. The seam brazed B shaped tubes are stronger than standard welded O style tubes, allowing thinner and lighter aluminum with better efficiency. This design creates dual liquid laminar flow inside each tube for improved heat rejection.

Features ultra efficient 5mm tall multi louvered fins, carefully aligned to maximize airflow and surface contact. End tanks are 100 percent TIG welded aluminum, no plastic, no crimped gaskets. The larger aluminum tanks increase fluid volume and durability under high pressure conditions.

CNC machined mounting brackets and aluminum mounting pins replace the weak OEM plastic mounting system. OEM style quick connect inlet and outlet connections allow reuse of factory or aftermarket hoses.

Finished in satin black for added corrosion protection and a clean OEM plus look behind the grilles. Includes a detachable rock guard for added protection against road debris. Individually leak and pressure tested before leaving the factory.

Replaces OEM Part Number 17118095285.

Configuration Options

Sold individually. All G8X applications use two auxiliary radiators.

Multi fit design works on both left and right side.

Right side radiator supports the charge air cooling system.

Left side radiator supports the engine cooling system.

You can upgrade one side at a time depending on your cooling goals.

Exhaust Tips & Customization

Not applicable. This upgrade focuses on cooling system performance and durability.

Production & Lead Time

Each radiator is built with strict quality control and pressure tested before shipping. Production time can vary depending on demand. Every unit is made with durability and performance in mind, not rushed for volume.

Fitment

Year Range	Make	Chassis Code	Model	Trim	Engine / Trans / Etc	Notes
2023-2025	BMW	G87	M2	-	Turbocharged 3.0L L6	-
2021-2025	BMW	G8X	M3	-	Turbocharged 3.0L L6	-
2021-2025	BMW	G8X	M3	Competition	Turbocharged 3.0L L6	-
2022-2025	BMW	G8X	M3	Competition xDrive	Turbocharged 3.0L L6	-
2024	BMW	G8X	M3	CS	Turbocharged 3.0L L6	-
2025	BMW	G8X	M3	CS	Turbocharged 3.0L L6	-
2021-2025	BMW	G8X	M4	-	Turbocharged 3.0L L6	-
2021-2025	BMW	G8X	M4	Competition	Turbocharged 3.0L L6	-
2021-2025	BMW	G8X	M4	Competition xDrive	Turbocharged 3.0L L6	-
2023-2025	BMW	G8X	M4	CSL	Turbocharged 3.0L L6	-

Benefits

• 2 row 42mm core for increased cooling capacity
• CSF exclusive B Tube technology for improved heat transfer
• 100 percent all aluminum TIG welded construction
• Larger tank volume than OEM plastic units
• Stronger aluminum mounting pins and brackets
• Multi fit left or right side compatibility
• Includes detachable rock guard
• True drop in fit with no modifications
• Individually leak and pressure tested
• 2 year limited warranty

NOTE: OFF ROAD USE ONLY